Queensland spends tens of millions to jail more children than any other jurisdiction in the nation but it's not making the community any safer, a report says.
There were 219 inmates under the age 17 in detention in June of this year compared to 172 in 2014, according to a Justice Reform Initiative report released on Tuesday.
Nine out of 10 haven't been sentenced, and two in three are Indigenous despite that cohort making up less than 10 per cent of the state's child population.
The Queensland government spends $1880 per day or about $686,127 per year to keep a child behind bars, with the overall youth detention cost totalling $183 million in 2021.
Justice Reform Initiative executive director Mindy Sotiri says the incarceration policy is based on "political, policy and legislative choices" rather than evidence.
"Building more prisons, as the Queensland government is planning to do with its proposed $500 million youth prison expansion, does not work to deter crime, rehabilitate or make communities safer," she said.
"This is a short-sighted and counterproductive policy that will make it more likely that vulnerable children will commit further offences and become trapped in the revolving prison door that has become a devastating feature of Queensland's justice system."
Children were held in solitary confinement for more than 12 hours on 30,000 occasions in the year to June, the report said.
Almost nine in 10 of those were Indigenous children.
The report said there were also 2860 instances were children under the age of 14 were held in solitary.
Corrections Minister Mark Ryan denied youth justice policies weren't working, saying detention was being used alongside other programs.
"When you detain them, you also have intervention programs, and that's what we're investing in and continue to invest in, and that's what we continue to remain committed to," he told reporters.
Many children who enter detention experience socioeconomic disadvantage, trauma, out-of-home care and neurological disorders, and "prison increases disadvantage and disconnection", the report said.
The state spends about $128 million each year on support programs for young inmates, but 94 per cent of children who enter them end up reoffending after being released.
The report said imprisoned young people - particularly Indigenous children - need programs to treat their physical and mental health, address their education, poverty, homelessness, and provide them with health and mental treatments.
"Children need family and community support, education, and life opportunities, not punishment that compounds disconnection and disadvantage," the Justice Reform Initiative wrote.
"A persistent failure to provide the kind of supports and opportunities in the community that genuinely address the underlying drivers of incarceration underpins a costly system that does not make the community safer."
The report also called for the age of criminal responsibility, or minimum age for detention in Queensland, to be raised from 10 to 14.
A state parliament committee earlier this year rejected a Greens push to lift the age to 14, arguing instead for a national push to make 12 the minimum age.
